This year I published a study of primate cortical cells with concentric receptive fields and double opponent-color properties. They are probably the first stage in the cortical integration of color information. Which types or types of geniculate fibers end on these cells? Multiple-unit studies in the striate cortex indicate that one possible input to the concentric color cells is a geniculate fiber with an excitatory-inhibitory center-surround field but connected with only one class of one (e.g., red). In other cases the afferents to the concentric cells appeared to be red-green Type II units. Are there Type III geniculate cells with one cone input or Type II cells with red-green opponent systems? Neither type of cell has been seen but no one has ever systematically looked for them. Perhaps these classes are found only in the foveal representation, which was not studied by Wiesel and Hubel but which I have examined at the cortical level. Because Wiesel and Hubel did not measure the spectral sensitivities of many cells, it is possible that some of their Type II and III units may have been of the red-green or of the single-cone variety, respectively. It will certainly be worth re-examining the spectral sensitivities of these neurons to test this idea.